Project Summary/Abstract Childhood maltreatment ? a form of trauma defined as the experience of emotional or physical abuse or neglect or sexual abuse before the age of 16 ? is an established risk factor for depression. Research also suggests childhood maltreatment is associated with unfavorable depression treatment outcomes, namely a lack of response and remission. Further, there is evidence to suggest that individuals who have experienced childhood maltreatment are at increased risk of depression recurrence. Despite the substantial body of literature that explores the relationship between childhood maltreatment and depression, we are not aware of any published studies investigating the relationship between childhood maltreatment and winter seasonal affective disorder (SAD), a prominent subtype of depression that impacts over 16 million individuals yearly in the United States. SAD involves major depression recurrence in the fall/winter months and spontaneous remission in the springtime. Efficacious treatments for SAD include light therapy (LT) and SAD- tailored cognitive behavioral therapy (CBT-SAD). An improved understanding of the relationship between childhood maltreatment and SAD treatment outcomes is critical for treatment optimization. This study generates new knowledge about the relationship between childhood maltreatment and SAD treatment outcomes through the following specific aims: AIM 1: Examine the impact of childhood maltreatment on depression recurrence, remission, and symptom severity during the next two winter seasons following SAD treatment. AIM 2: Determine whether childhood maltreatment predicts a differential acute treatment response to CBT-SAD or light therapy as measured by symptom severity and remission status post-treatment. The project will collect information on the various domains of childhood maltreatment (emotional abuse, physical abuse, emotional neglect, physical neglect, sexual abuse) at baseline using the Childhood Trauma Questionnaire, and will assess the impact of these forms of childhood maltreatment on SAD treatment outcomes at post-treatment and at one and two winters following treatment. This work has valuable public health implications, as a better understanding of which SAD treatment is optimal for individuals who endorse childhood maltreatment is a first step to aid clinician decision-making and facilitate precision medicine, thereby improving both patient outcomes and healthcare cost effectiveness.